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Spring安装基本属性的原理分析与代码实现

网友分享于:2013-11-20  浏览:2次
Spring装配基本属性的原理分析与代码实现

首先,做一个配置属性的基本测试。修改beans.xml,使引用外部类变成内部bean属性:

<?xml version="1.0" encoding="UTF-8"?>

<beans xmlns="http://www.springframework.org/schema/beans"

       xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"

       xsi:schemaLocation="http://www.springframework.org/schema/beans

           http://www.springframework.org/schema/beans/spring-beans-2.5.xsd">

         <bean id="peopleDao" class="com.wxy.dao.impl.PeopleDaoBean"></bean>

         <bean id="peopleService" class="com.wxy.service.impl.PeopleServiceBean">

                  <property name="peopleDao" ref=” peopleDao”/>

                 

         </bean>

</beans>

 

  测试:

public class Test {

 

    public static void main(String[] args) {

        //IOC容器实例化

        ClassPathXmlApplicationContext ac = new ClassPathXmlApplicationContext("beans.xml");

        PeopleService peopleService = (PeopleService) ac.getBean("peopleService");

        peopleService.save();

    }

 

}

    结果正常!能够引用得到(这不是废话么) 

   使用refref所指向的bean可以被多个bean引用;ref依赖对象将作为一个属性被注入。

  

 

Spring是如何实现装配基本属性的呢?下面用源码模拟实现之:

 

1 xml配置文件中增加属性:

<?xml version="1.0" encoding="UTF-8"?>

<beans xmlns="http://www.springframework.org/schema/beans"

       xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"

       xsi:schemaLocation="http://www.springframework.org/schema/beans

           http://www.springframework.org/schema/beans/spring-beans-2.5.xsd">

         <!--  <bean id="peopleDao" class="com.wxy.dao.impl.PeopleDaoBean"></bean>-->

         <bean id="peopleService" class="com.wxy.service.impl.PeopleServiceBean">

                    <property name="peopleDao" ref="com.wxy.dao.impl.PeopleDaoBean"/>

                    <property name="name" value="wxy"/>

                    <property name="id" value="218"/>

         </bean>

</beans>

    

2、在属性BeanPorpertyDefinition中定义相应的属性,用来存放xml文件中定义的属性:

package com.wxy.bean;

 

/**

*   存放beanproperty属性

* 

*   @creator            xiaoyu.wang  

*   @create-time     2011-8-10   下午04:40:07  

*   @revision          $Id

*/

public class PropertyDefinition {

 

    private String name; //属性名

    private String ref;  //属性依赖对象

    private String value;

 

    /**

     * @return the name

     */

    public String getName() {

        return name;

    }

 

    /**

     * @param name the name to set

     */

    public void setName(String name) {

        this.name = name;

    }

 

    /**

     * @return the ref

     */

    public String getRef() {

        return ref;

    }

 

    /**

     * @param ref the ref to set

     */

    public void setRef(String ref) {

        this.ref = ref;

    }

 

    public PropertyDefinition(String name, String ref, String value) {

        super();

        this.name = name;

        this.ref = ref;

        this.value = value;

    }

 

    /**

     * @return the value

     */

    public String getValue() {

        return value;

    }

 

    /**

     * @param value the value to set

     */

    public void setValue(String value) {

        this.value = value;

    }

 

    /* (non-Javadoc)

     * @see java.lang.Object#toString()

     */

    @Override

    public String toString() {

        return "PropertyDefinition [name=" + name + ", ref=" + ref + ", value=" + value + "]";

    }

 

}

   

3 修改PeopelServiceBean ,添加相对应的属性:

 public class PeopleServiceBean implements PeopleService {

 

    private PeopleDao peopleDao;

    private String    name;

    private Integer   id;

 

    /**

     * @return the peopleDao

     */

    public PeopleDao getPeopleDao() {

        return peopleDao;

    }

 

    /**

     * @param peopleDao the peopleDao to set

     */

    public void setPeopleDao(PeopleDao peopleDao) {

        this.peopleDao = peopleDao;

    }

 

    /**

     * @return the name

     */

    public String getName() {

        return name;

    }

 

    /**

     * @param name the name to set

     */

    public void setName(String name) {

        this.name = name;

    }

 

    /**

     * @return the id

     */

    public Integer getId() {

        return id;

    }

 

    /**

     * @param id the id to set

     */

    public void setId(Integer id) {

        this.id = id;

    }

 

    public void save() {

 

        System.out.println("--> the method is called save()! name=" + name + ",id=" + id);

        peopleDao.add();

    }

 

}

  

4、读取属性值,修改WxyClassPathXMLApplicationContext.java, 添加注入属性功能  

package com.wxy.content;

 

import java.beans.IntrospectionException;

import java.beans.Introspector;

import java.beans.PropertyDescriptor;

import java.lang.reflect.InvocationTargetException;

import java.lang.reflect.Method;

import java.net.URL;

import java.util.ArrayList;

import java.util.HashMap;

import java.util.List;

import java.util.Map;

 

import org.apache.commons.beanutils.ConvertUtils;

import org.dom4j.Document;

import org.dom4j.Element;

import org.dom4j.XPath;

import org.dom4j.io.SAXReader;

 

import com.wxy.bean.BeanDefinition;

import com.wxy.bean.PropertyDefinition;

 

/**

*  自定义IoC容器

*  BeanDefinitionresource定位:readXML();

*  BeanDefinition的载入和解析 :readXML();

*  BeanDefinitionIoC容器中的注册 instanceBeans();

*   @create-time     2011-8-10   上午09:19:17  

*   @revision          $Id

*/

public class WxyClassPathXMLApplicationContext {

 

    //存放BeanDefinition的列表,在beans.xml中定义的bean可能不止一个

    private final List<BeanDefinition> beanDefines = new ArrayList<BeanDefinition>();

    //将类名作为索引,将创建的Bean对象存入到Map

    private final Map<String, Object>  sigletons   = new HashMap<String, Object>();

 

    public WxyClassPathXMLApplicationContext(String fileName) {

        //读取xml配置文件

        this.readXML(fileName);

        //实例化bean

        this.instanceBeans();

        //注入对象

        this.injectObject();

    }

 

    /**

     *bean对象的属性注入值

     */

    private void injectObject() {

        for (BeanDefinition beanDefinition : beanDefines) {

            //获取beanDefines中的对象

            Object bean = sigletons.get(beanDefinition.getId());

            if (bean != null) {

                //如果存在,利用反射技术将值注入

                try {

                    //获取Bean的描述属性类

                    PropertyDescriptor[] ps = Introspector.getBeanInfo(bean.getClass())

                        .getPropertyDescriptors();

                    for (PropertyDefinition propertyDefinition : beanDefinition.getProperties()) {

                        for (PropertyDescriptor properdesc : ps) {

                            //取得属性名字与propertyDefinition中的属性做比较

                            if (propertyDefinition.getName().equals(properdesc.getName())) {

                                //获得属性的setter方法

                                Method setter = properdesc.getWriteMethod();

                                if (setter != null) {

 

                                    Object value = null;

                                    if (propertyDefinition.getRef() != null

                                        && !propertyDefinition.getRef().isEmpty()) {//注入依赖对象

                                        value = sigletons.get(propertyDefinition.getRef());

                                    } else {//注入基本类型

                                        //将字符串类型装换成用户需要的类型,需要用到jar包中的commons-beanutils.jar

                                        value = ConvertUtils.convert(propertyDefinition.getValue(),

                                            properdesc.getPropertyType());

                                    }

                                    //允许访私有方法

                                    setter.setAccessible(true);

                                    //把引用对象注入到属性

                                    setter.invoke(bean, value);

                                }

                            }

                        }

                    }

                } catch (SecurityException e) {

                    // TODO Auto-generated catch block

                    e.printStackTrace();

                } catch (IllegalArgumentException e) {

                    // TODO Auto-generated catch block

                    e.printStackTrace();

                } catch (IntrospectionException e) {

                    // TODO Auto-generated catch block

                    e.printStackTrace();

                } catch (IllegalAccessException e) {

                    // TODO Auto-generated catch block

                    e.printStackTrace();

                } catch (InvocationTargetException e) {

                    // TODO Auto-generated catch block

                    e.printStackTrace();

                }

            }

        }

    }

 

    /**

     * 读取XML配置文件,获取BeanDefinition内容,存入到beanDefinition列表中

     * @param fileName xml配置文件名称

     */

 

    private void readXML(String fileName) {

        SAXReader saxReader = new SAXReader();

        Document document = null;

        try {

            //通过类加载器获取Resource资源路径,实现BeanDefinitionresource定位

            URL xmlPath = this.getClass().getClassLoader().getResource(fileName);

            //xml读入到document

            document = saxReader.read(xmlPath);

            Map<String, String> nsMap = new HashMap<String, String>();

            //加入命名空间

            nsMap.put("ns", "http://www.springframework.org/schema/beans");

            //创建beans/bean查询路径,注意:路径前要注明命名空间,便于解析

            XPath xsub = document.createXPath("//ns:beans/ns:bean");

            //设置命名空间

            xsub.setNamespaceURIs(nsMap);

            //获取文档下的所有Bean节点

            List<Element> beans = xsub.selectNodes(document);

            for (Element element : beans) {

                //获取id属性值

                String id = element.attributeValue("id");

                //获取class属性值

                String clazz = element.attributeValue("class");

                BeanDefinition beanDefinition = new BeanDefinition(id, clazz);

                //创建bean/property查询路径

                XPath propertysub = element.createXPath("ns:property");

                //设置命名空间

                propertysub.setNamespaceURIs(nsMap);

                //获取beanproperty列表节点

                List<Element> properties = propertysub.selectNodes(element);

                for (Element property : properties) {

                    String propertyName = property.attributeValue("name");

                    String propertyref = property.attributeValue("ref");

                    String propertyValue = property.attributeValue("value");

                    PropertyDefinition propertyDefinition = new PropertyDefinition(propertyName,

                        propertyref, propertyValue);

                    System.out.println(property);

                    //property属性添加到beanDefinition

                    beanDefinition.getProperties().add(propertyDefinition);

                }

                //将新创建的BeanDefinition赌侠ing放入到BeanDeifnitions

                beanDefines.add(beanDefinition);

            }

        } catch (Exception e) {

            System.out.println(e.toString());

        }

    }

 

    /**

     * 实例化bean,存入到sigletons

     */

    private void instanceBeans() {

        for (BeanDefinition beanDefinition : beanDefines) {

            try {

                if (beanDefinition.getClassName() != null

                    && !(beanDefinition.getClassName().isEmpty())) {

                    //利用java反射机制,生成BeanDefinition实例,并将其注册到sigletons

                    sigletons.put(beanDefinition.getId(), Class.forName(

                        beanDefinition.getClassName()).newInstance());

                }

            } catch (Exception e) {

                e.printStackTrace();

            }

        }

 

    }

 

    /**

     * 根据ID名获取实例bean

     * return 返回一个Object对象,用户使用时,需要对获取的结果进行转换类型

     */

    public Object getBean(String beanName) {

        return this.sigletons.get(beanName);

    }

}

  

5 进行测试:

public class MyTest {

 

    public static void main(String[] args) {

        //MyIOC容器实例化

        WxyClassPathXMLApplicationContext ac = new WxyClassPathXMLApplicationContext("beans.xml");

        PeopleService peopleService = (PeopleService) ac.getBean("peopleService");

        peopleService.save();

    }

 

}

  

6 测试结果:

--> the method is called save()! name=wxy,id=218

this is the method PeopleDaoBean.add()!

  

 

 

 

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